Magnetoresistance effect device and high frequency device

ABSTRACT

Provided is a magnetoresistance effect device that functions as a high frequency device such as a high frequency filter or the like. The magnetoresistance effect device includes a magnetoresistance effect element having a first ferromagnetic layer, a second ferromagnetic layer, and a spacer layer sandwiched between the first ferromagnetic layer and the second ferromagnetic layer, a first signal line configured to generate a high frequency magnetic field as a high frequency current flows, a direct current application terminal to which a power supply is able to be connected to cause a direct current to flow to the magnetoresistance effect element in a lamination direction, and an independent magnetic body configured to receive a high frequency magnetic field generated in the first signal line to oscillate magnetization and apply a magnetic field generated through the magnetization to the magnetoresistance effect element.

BACKGROUND OF THE INVENTION Field of the Invention

The present disclosure relates to a magnetoresistance effect device anda high frequency device.

Priority is claimed on Japanese Patent Application No. 2017-172713,filed on Sep. 8, 2017, and Japanese Patent Application No. 2018-151676,filed Aug. 10, 2018, the content of which are incorporated herein byreference.

Description of Related Art

In recent years, according to the enhanced functionality of mobilecommunication terminals such as cellular phones or the like, an increasein speed of wireless communication has progressed. Since thecommunication speed is proportional to a bandwidth of a frequency used,a frequency band required for communication has increased. Accordingly,the number of mounted high frequency filters required for a mobilecommunication terminal has increased.

In addition, spintronics has recently been researched as a technologythat may be able to be applied to new high frequency components. One ofphenomena attracting attention regarding this is a ferromagneticresonance phenomenon of a magnetoresistance effect element (seeNon-Patent Document 1).

When an alternating magnetic field is applied to a magnetoresistanceeffect element, a ferromagnetic resonance can occur in themagnetoresistance effect element. When the ferromagnetic resonanceoccurs, a resistance value of the magnetoresistance effect elementperiodically oscillates at a frequency corresponding to a ferromagneticresonance frequency (hereinafter, referred to as a resonance frequency).The resonance frequency of the magnetoresistance effect element variesaccording to an intensity of a magnetic field applied to themagnetoresistance effect element, and in general, the resonancefrequency is a high frequency band of several to several tens of GHz.

CITATION LIST Patent Documents

Non-Patent Document 1

J. M. L. Beaujour et al., JOURNAL OF APPLIED PHYSICS 99, 08N503 (2006).

SUMMARY OF THE INVENTION

As described above, research on high frequency oscillation elementsusing a ferromagnetic resonance phenomenon is proceeding. However, thereis still insufficient specific research on the ferromagnetic resonancephenomenon and other applications.

In consideration of the above-mentioned problems, the present disclosureis directed to providing a magnetoresistance effect device whichfunctions as a high frequency device such as a high frequency filter orthe like using a ferromagnetic resonance phenomenon.

In order to solve the problems, a method of using a magnetoresistanceeffect device that uses a ferromagnetic resonance phenomenon as a highfrequency device was examined. The result was that a magnetoresistanceeffect device utilizing a resistance value of a magnetoresistance effectelement temporally varying due to a ferromagnetic resonance phenomenonwas found, and it was found that the magnetoresistance effect devicefunctions as a high frequency device.

In addition, it was found that, when an independent magnetic body isinstalled, noise due to thermal fluctuation or the like can be reduced,and a magnetoresistance effect device having good output characteristicscan be obtained.

That is, the present disclosure provides the following means in order tosolve the above problems.

(1) A magnetoresistance effect device according to a first aspectincludes a magnetoresistance effect element having a first ferromagneticlayer, a second ferromagnetic layer, and a spacer layer sandwichedbetween the first ferromagnetic layer and the second ferromagneticlayer; a first signal line configured to generate a high frequencymagnetic field when a high frequency current flows; a direct currentapplication terminal to which a power supply is able to be connected tocause a direct current to flow to the magnetoresistance effect elementin a lamination direction; and an independent magnetic body configuredto receive a high frequency magnetic field generated in the first signalline to oscillate magnetization and apply a magnetic field generatedthrough the magnetization to the magnetoresistance effect element.

(2) In the magnetoresistance effect device according to the aspect, aresonance frequency of the independent magnetic body may be smaller thana resonance frequency of the first ferromagnetic layer and the secondferromagnetic layer.

(3) The magnetoresistance effect device according to the aspect mayfurther include a low pass filter configured to reduce a part of asignal output to the outside, wherein the low pass filter may allow afrequency smaller than the resonance frequency of the firstferromagnetic layer and the second ferromagnetic layer to passtherethrough.

(4) In the magnetoresistance effect device according to the aspect, avolume of the independent magnetic body may be 100 times or more avolume of the first ferromagnetic layer or the second ferromagneticlayer.

(5) In the magnetoresistance effect device according to the aspect, adamping constant of the independent magnetic body may be 0.005 or less.

(6) In the magnetoresistance effect device according to the aspect, theindependent magnetic body may be an insulating material.

(7) In the magnetoresistance effect device according to the aspect, theindependent magnetic body may be an electrical conductor.

(8) The magnetoresistance effect device according to the aspect mayfurther include a magnetic field application mechanism configured toapply an external magnetic field to the independent magnetic body, andmodulate a resonance frequency of at least one of the independentmagnetic body, the first ferromagnetic layer and the secondferromagnetic layer.

(9) The magnetoresistance effect device according to the aspect mayfurther include a bias magnetic layer configured to apply an externalmagnetic field to the first ferromagnetic layer or the secondferromagnetic layer of the magnetoresistance effect element, andmodulate a resonance frequency of the first ferromagnetic layer or thesecond ferromagnetic layer.

(10) The magnetoresistance effect device according to the aspect mayhave a plurality of magnetoresistance effect elements, and a pluralityof magnetoresistance effect elements may be disposed with respect to theone independent magnetic body.

(11) The magnetoresistance effect device according to the aspect mayhave a plurality of magnetoresistance effect elements and a plurality ofindependent magnetic bodies, and each independent magnetic body may bedisposed with respect to one magnetoresistance effect element,respectively.

(12) In the magnetoresistance effect device according to the aspect, atleast some of the plurality of magnetoresistance effect elements may bearranged parallel to each other.

(13) In the magnetoresistance effect device according to the aspect, atleast some of the plurality of magnetoresistance effect element may bearranged in series.

(14) In the magnetoresistance effect device according to the aspect,each of the plurality of magnetoresistance effect elements may have anoutput signal line through which a high frequency current output fromthe magnetoresistance effect element flows, and at least one of theoutput signal lines may be disposed at a position where a high frequencymagnetic field is applied to the independent magnetic body configured toapply a magnetic field to at least one of the plurality ofmagnetoresistance effect elements.

(15) A high frequency device according to a second aspect uses themagnetoresistance effect device according to the aspect.

According to the magnetoresistance effect device of the aspect, themagnetoresistance effect device using a ferromagnetic resonancephenomenon may be used as a high frequency device such as a highfrequency filter, an amplifier, or the like.

In addition, according to the magnetoresistance effect device accordingto the aspect, a resistance value variation of the magnetoresistanceeffect element is greatly affected by oscillation of magnetization ofthe independent magnetic body having a large magnetic moment. For thisreason, occurrence of noise generated due to oscillation of themagnetization of the first ferromagnetic layer and the secondferromagnetic layer due to thermal fluctuation can be decreased.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view showing a magnetoresistance effect deviceaccording to a first embodiment.

FIG. 2 is a view showing a relation of an oscillation amplitude and anoutput signal with respect to a period of a high frequency magneticfield applied to an independent magnetic body and a magnetization freelayer when a resonance frequency of the independent magnetic bodycoincides with a resonance frequency of the magnetization free layer.

FIG. 3 is a view showing a relation of an oscillation amplitude and anoutput signal with respect to a period of a high frequency magneticfield applied to the independent magnetic body and the magnetizationfree layer when a resonance frequency of the independent magnetic bodyis different from a resonance frequency of the magnetization free layer.

FIG. 4 is a view showing a relation between a frequency of a highfrequency signal input to the magnetoresistance effect device and anamplitude of a voltage output from the magnetoresistance effect devicewhen a direct current applied to the magnetoresistance effect element isconstant.

FIG. 5 is a view showing a relation between a frequency of a highfrequency signal input to the magnetoresistance effect device and anamplitude of a voltage output from the magnetoresistance effect devicewhen an external magnetic field applied to the magnetoresistance effectelement is constant.

FIG. 6 is a view schematically showing an example of a circuitconfiguration of a magnetoresistance effect device including a pluralityof magnetoresistance effect elements.

FIG. 7 is a view schematically showing another example of a circuitconfiguration of a magnetoresistance effect device including a pluralityof magnetoresistance effect elements.

FIG. 8 is a view schematically showing another example of a circuitconfiguration of a magnetoresistance effect device including a pluralityof magnetoresistance effect elements.

FIG. 9 is a perspective view of another example of a circuitconfiguration of magnetoresistance effect device including a pluralityof magnetoresistance effect elements.

FIG. 10 is a view schematically showing an example of a circuitconfiguration of a magnetoresistance effect device in which a pluralityof magnetoresistance effect elements and a plurality of independentmagnetic bodies are provided, and one independent magnetic body isinstalled with respect to one magnetoresistance effect element.

FIG. 11 is a view schematically showing another example of a circuitconfiguration of a magnetoresistance effect device including a pluralityof magnetoresistance effect elements.

FIG. 12 is a view schematically showing another example of a circuitconfiguration of a magnetoresistance effect device including a pluralityof magnetoresistance effect elements.

FIG. 13 is an enlarged schematic view of a major part of amagnetoresistance effect device of Example 1.

FIG. 14 shows a result of an output voltage of the magnetoresistanceeffect device according to Example 1.

FIG. 15 shows a result of a noise output electric power of themagnetoresistance effect device according to Example 1.

FIG. 16 is an enlarged schematic view of a major part of amagnetoresistance effect device of Comparative example 1.

FIG. 17 shows a result of an output voltage of the magnetoresistanceeffect device according to Comparative example 1.

FIG. 18 shows a result of a noise output electric power of themagnetoresistance effect device according to Comparative example 1.

FIG. 19 shows a result of an output voltage of a magnetoresistanceeffect device according to Comparative example 2.

FIG. 20 shows a result of a noise output electric power of themagnetoresistance effect device according to Comparative example 2.

FIG. 21 shows a result of an output voltage of a magnetoresistanceeffect device according to Example 2.

FIG. 22 shows a result of a noise output electric power of themagnetoresistance effect device according to Example 2.

FIG. 23 is an enlarged schematic view of a major part of amagnetoresistance effect device of Example 3.

FIG. 24 shows a result of an output voltage of the magnetoresistanceeffect device according to Example 3.

FIG. 25 shows a result of a noise output electric power of themagnetoresistance effect device according to Example 3.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, a magnetoresistance effect device will be described indetail with reference to the accompanying drawings. The drawings used inthe following description may be shown by enlarging feature parts forthe sake of convenience to make the feature parts easier to understand,and dimensional proportions of components may be different from actualones. Materials, dimensions, or the like, exemplarily shown in thefollowing description are examples, and the present disclosure is notlimited thereto and may be appropriately modified and embodied withoutdeparting from the spirit of the present disclosure.

First Embodiment

FIG. 1 is a schematic view showing a circuit configuration of amagnetoresistance effect device according to a first embodiment. Amagnetoresistance effect device 100 shown in FIG. 1 has amagnetoresistance effect element 10, a first signal line 20, a directcurrent application terminal 40 and an independent magnetic body 60. Themagnetoresistance effect device 100 inputs a signal from a first port 1and outputs a signal from a second port 2. The output signal can bemodulated by a magnetic field application mechanism 50.

<First Port and Second Port>

The first port 1 is an input terminal of the magnetoresistance effectdevice 100. The first port 1 corresponds to one end of the first signalline 20. An alternating current signal can be applied to themagnetoresistance effect device 100 by connecting an alternating currentsignal source (not shown) to the first port 1.

The second port 2 is an output terminal of the magnetoresistance effectdevice 100. The second port 2 corresponds to one end of an output signalline (a second signal line) 30 that transmits a signal output from themagnetoresistance effect element 10. A signal output from themagnetoresistance effect device 100 can be measured by connecting a highfrequency measuring instrument (not shown) to the second port 2. Forexample, a network analyzer or the like can be used in the highfrequency measuring instrument.

<Magnetoresistance Effect Element>

The magnetoresistance effect element 10 has a first ferromagnetic layer11, a second ferromagnetic layer 12 and a spacer layer 13. The spacerlayer 13 is disposed between the first ferromagnetic layer 11 and thesecond ferromagnetic layer 12. Hereinafter, a direction of magnetizationof the first ferromagnetic layer 11 and a direction of magnetization ofthe second ferromagnetic layer 12 relatively vary to function as themagnetoresistance effect element 10. The first ferromagnetic layer 11and the second ferromagnetic layer 12 may have a configuration in whicha magnetization, with respect to a magnetization of one fixed side, ofthe other side varies (a configuration in which one side is themagnetization fixed layer and the other side is the magnetization freelayer), or may have a configuration in which directions of magnetizationof both sides respectively vary (a configuration in which both sides arereferred to as magnetization free layers) in a predetermined magneticfield environment. In either of these cases, since the two directions ofthe magnetization are relatively varied, a resistance value variationoccurs. Hereinafter, a case in which the first ferromagnetic layer 11 isthe magnetization fixed layer and the second ferromagnetic layer 12 isthe magnetization free layer will be exemplarily described.

The magnetization fixed layer 11 is formed of a ferromagnetic material.The magnetization fixed layer 11 is preferably formed of a high spinpolarization material such as Fe, Co, Ni, an alloy of Ni and Fe, analloy of Fe and Co, an alloy of Fe, Co and B, or the like. When thesematerials are used, a rate of change of magnetoresistance of themagnetoresistance effect element 10 is increased. In addition, themagnetization fixed layer 11 may be formed of a Heusler alloy. A filmthickness of the magnetization fixed layer 11 is preferably 1 to 10 nm.

A magnetization fixing method of the magnetization fixed layer 11 is notparticularly limited. For example, an antiferromagnetic layer may beadded to come in contact with the magnetization fixed layer 11 in orderto fix the magnetization of the magnetization fixed layer 11. Inaddition, the magnetization of the magnetization fixed layer 11 may befixed using magnetic anisotropy due to a crystal structure, a shape, orthe like. FeO, CoO, NiO, CuFeS₂, IrMn, FeMn, PtMn, Cr, Mn, or the like,may be used in the antiferromagnetic layer.

The magnetization free layer 12 is formed of a ferromagnetic materialhaving a magnetization direction that can be varied by an appliedmagnetic field or spin-polarized electrons from the outside.

The magnetization free layer 12 can use CoFe, CoFeB, CoFeSi, CoMnGe,CoMnSi, CoMnAl, or the like, as a material when an easy axis ofmagnetization is provided in an in-plane direction perpendicular to alamination direction in which the magnetization free layer 12 islaminated, or can use Co, a CoCr-based alloy, a Co multilayer film, aCoCrPt-based alloy, a FePt-based alloy, a SmCo-based alloy containingrare earth elements, a TbFeCo alloy, or the like, as a material when aneasy axis of magnetization is provided in the lamination direction ofthe magnetization free layer 12. In addition, the magnetization freelayer 12 may be formed of a Heusler alloy.

A thickness of the magnetization free layer 12 is preferably about 1 to10 nm. In addition, a high spin polarization material may be insertedbetween the magnetization free layer 12 and the spacer layer 13. When ahigh spin polarization material is inserted, a high rate of change ofmagnetoresistance can be obtained.

A CoFe alloy, a CoFeB alloy, or the like, may be exemplified as the highspin polarization material. A film thickness of either a CoFe alloy or aCoFeB alloy is preferably about 0.2 to 1.0 nm.

The spacer layer 13 is a non-magnetic layer disposed between themagnetization fixed layer 11 and the magnetization free layer 12. Thespacer layer 13 is constituted by a layer formed of an electricconductor, an insulating material or a semiconductor, or a layerincluding an electrical conduction point formed of a conductor in aninsulating material.

For example, the magnetoresistance effect element 10 may be a tunnelingmagnetoresistance (TMR) element when the spacer layer 13 is formed of aninsulating material, and the magnetoresistance effect element 10 may bea giant magnetoresistance (GMR) element when the spacer layer 13 isformed of a metal.

When the spacer layer 13 is formed of a non-magnetic conductivematerial, a conductive material such as Cu, Ag, Au, Ru, or the like, canbe used. In order to efficiently use a GMR effect, a film thickness ofthe spacer layer 13 is preferably about 0.5 to 3.0 nm.

When a non-magnetic insulating material is applied for the spacer layer13, Al₂O₃, MgO, or the like, is exemplified as a material therefor, anda tunneling magnetoresistance (TMR) effect appears in themagnetoresistance effect element 10. A high rate of change ofmagnetoresistance is obtained by adjusting a film thickness of thespacer layer 13 such that a coherent tunnel effect appears between themagnetization fixed layer 11 and the magnetization free layer 12. Whenthe TMR effect is used, a film thickness of the spacer layer 13 ispreferably about 0.5 to 3.0 nm.

When the spacer layer 13 is formed of a non-magnetic semiconductormaterial, a material such as ZnO, In₂O₃, SnO₂, ITO, GaO_(x), Ga₂O_(x),or the like, may be used. In this case, a film thickness of the spacerlayer 13 is preferably about 1.0 to 4.0 nm.

When a layer including an electrical conduction point constituted by aconductor in a non-magnetic insulating material is applied as the spacerlayer 13, a structure including an electrical conduction pointconstituted by a conductor such as CoFe, CoFeB, CoFeSi, CoMnGe, CoMnSi,CoMnAl, Fe, Co, Au, Cu, Al, Mg, or the like, in a non-magneticinsulating material formed of Al₂O₃ or MgO is preferably provided. Inthis case, a film thickness of the spacer layer 13 is preferably about0.5 to 2.0 nm.

In order to increase conductivity with respect to the magnetoresistanceeffect element 10, electrodes are preferably installed on both surfacesof the magnetoresistance effect element 10 in the lamination direction.Hereinafter, an electrode installed on a section below themagnetoresistance effect element 10 in the lamination direction isreferred to as a lower electrode 14, and an electrode installed on asection thereabove is referred to as an upper electrode 15. When thelower electrode 14 and the upper electrode 15 are installed, contact ofthe magnetoresistance effect element 10 with the output signal line 30and a third signal line 31 is on a plane, and a flow of a signal(current) is in a lamination direction at any position in the in-planedirection of the magnetoresistance effect element 10.

The lower electrode 14 and the upper electrode 15 are formed of amaterial having conductivity. For example, Ta, Cu, Au, AuCu, Ru, or thelike, may be used in the lower electrode 14 and the upper electrode 15.

In addition, a cap layer, a seed layer or a buffer layer may be disposedbetween the magnetoresistance effect element 10 and the lower electrode14 or the upper electrode 15. Ru, Ta, Cu, Cr, a lamination film thereof,or the like, is exemplified as the cap layer, the seed layer or thebuffer layer. A film thickness of each of the layers is preferably about2 to 10 nm.

The magnetoresistance effect element 10 has a long side that ispreferably 300 nm or less with regard to size when a shape of themagnetoresistance effect element 10 when seen in a plan view is arectangular shape (including a square shape). When the shape of themagnetoresistance effect element 10 when seen in the plan view is not arectangular shape, a long side of a rectangular shape that circumscribesthe shape of the magnetoresistance effect element 10 when seen in theplan view with a minimum area is defined as a long side of themagnetoresistance effect element 10.

When the long side is as small as about 300 nm, a volume of themagnetization free layer 12 is reduced, and a high-efficiencyferromagnetic resonance phenomenon can be realized. Here, “the shapewhen seen in a plan view” is a shape of each layer that constitutes themagnetoresistance effect element 10 seen from the lamination direction.

<First Signal Line>

The first signal line 20 in FIG. 1 has one end that is connected to thefirst port 1, and the other end that is connected to a referencepotential. In FIG. 1, the other end is connected to the ground G as thereference potential. A high frequency current flows through the firstsignal line 20 according to a potential difference between a highfrequency signal input to the first port 1 and the ground G When a highfrequency current flows through the first signal line 20, a highfrequency magnetic field is generated from the first signal line 20. Thehigh frequency magnetic field is applied to the independent magneticbody 60 and the magnetoresistance effect element 10.

The first signal line 20 is not limited to one signal line and may be aplurality of signal lines. In this case, the plurality of signal line ispreferably disposed at positions where high frequency magnetic fieldsgenerated from the signal lines are strengthened at a position of theindependent magnetic body 60.

In addition, the reference potential to which the first signal line 20is connected is not particularly limited to the ground G. For example, aconfiguration in which the first signal line 20 is connected to themagnetization fixed layer 11 of the magnetoresistance effect element 10and a part of the first signal line 20 functions as the lower electrode14 may be provided. In addition, a configuration in which the firstsignal line 20 is connected to the magnetization free layer 12 and thefirst signal line 20 functions as a part of the upper electrode 15 maybe provided.

<Output Signal Line, Third Signal Line>

The output signal line 30 propagates a signal output from themagnetoresistance effect element 10. The signal output from themagnetoresistance effect element 10 is a signal having a frequencyselected using a ferromagnetic resonance of the magnetoresistance effectelement 10. The output signal line 30 in FIG. 1 has one end that isconnected to the magnetoresistance effect element 10, and the other endthat is connected to the second port 2. That is, the output signal line30 in FIG. 1 connects the magnetoresistance effect element 10 and thesecond port 2.

The third signal line 31 has one end that is connected to themagnetoresistance effect element 10, and the other end that is connectedto a reference potential. While the third signal line 31 is connected tothe ground G that is shared with the reference potential of the firstsignal line 20 in FIG. 1, the third signal line 31 may be connected toanother reference potential. In order to simplify a circuitconfiguration, the reference potential of the third signal line 31 ispreferably shared with the reference potential of the first signal line20.

A form of each of the signal lines and the ground G is preferablydefined as a micro strip line (MSL) type or a coplanar waveguide (CPW)type. When the signal lines and the ground G are designed as a microstrip line (MSL) type or a coplanar waveguide (CPW) type, a signal linewidth or a ground distance is preferably designed such that acharacteristic impedance of the signal line and an impedance of acircuit system are equal to each other. A transmission loss of thesignal line can be minimized when the signal lines and the ground G aredesigned in this way.

<Direct Current Application Terminal>

The direct current application terminal 40 is connected to a powersupply 41, and applies a direct current or a direct current voltage tothe magnetoresistance effect element 10 in the lamination direction. Thepower supply 41 may be constituted by a circuit obtained by combining afixed resistor and a direct current voltage source, which can generate aconstant direct current. In addition, the power supply 41 may be adirect current source or may be a direct current voltage source.

An inductor 42 is disposed between the direct current applicationterminal 40 and the output signal line 30. The inductor 42 allows only adirect current component of the current to pass therethrough whileblocking high frequency components of the current. An output signaloutput from the magnetoresistance effect element 10 by the inductor 42efficiently flows to the second port 2. In addition, a direct current ofthe inductor 42 flows to a closed circuit constituted by the powersupply 41, the output signal line 30, the magnetoresistance effectelement 10, the third signal line 31 and the ground G.

A chip inductor, an inductor constituted by a pattern line, a resistiveelement having an inductor component, or the like, may be used in theinductor 42. An inductance of the inductor 42 is preferably 10 nH ormore.

<Independent Magnetic Body>

The independent magnetic body 60 is a magnetic body that is presentindependently from other circuit components. The magnetization of theindependent magnetic body 60 is oscillated (precesses) by receiving ahigh frequency magnetic field generated in the first signal line 20. Themagnetization of the independent magnetic body 60 generates a magneticfield and exerts an influence on the magnetization of the magnetizationfree layer 12 of the magnetoresistance effect element 10. Theindependent magnetic body 60 has a role of transmitting a signal fromthe first signal line 20 to the magnetoresistance effect element 10, andcan amplify the signal from the first signal line 20.

The independent magnetic body 60 is formed of a magnetic material. Theindependent magnetic body 60 is preferably a magnetic body including aninsulating material. For example, ceramics such as ferrite or the likemay be used. When the independent magnetic body 60 has an insulatingproperty, a short circuit to the first signal line 20 or themagnetoresistance effect element 10 can be prevented. Further, even whenthe independent magnetic body 60 is a metal or an alloy havingconductivity, a short circuit can be prevented by forming an insulatinglayer between the members.

When the independent magnetic body 60 has conductivity, the independentmagnetic body 60 may be a magnetic body having a soft magnetic body. Forexample, a magnetic material having a relatively large saturationmagnetization Ms and a relatively small coercive force such as Fe, Co,Ni, an alloy of Ni and Fe, an alloy of Fe and Co, or the like, may beused. Since the magnetization of the independent magnetic body 60 isgreatly oscillated by receiving the high frequency magnetic fieldgenerated in the first signal line 20. In addition, the saturationmagnetization Ms is large. A large magnetic field corresponding to thesignal flowing through the first signal line 20 can be provided to themagnetization of the magnetization free layer 12 of themagnetoresistance effect element 10.

In addition, when the independent magnetic body 60 has conductivity, theindependent magnetic body 60 may be a magnetic body having a hardmagnetic body. For example, a magnetic material having a largesaturation magnetization Ms and a large coercive force, such as a CoPtalloy, a FePt alloy, a CoCrPt alloy, or the like, may be used. Whileoscillation of the magnetization of the independent magnetic body 60 issmall because the coercive force is large even when the high frequencymagnetic field generated in the first signal line 20 is received, sincethe saturation magnetization Ms can be increased, a large magnetic fieldcorresponding to the signal flowing through the first signal line 20 canbe provided to the magnetization of the magnetization free layer 12 ofthe magnetoresistance effect element 10 as a whole.

In addition, a damping constant of the independent magnetic body 60 ispreferably 0.005 or less. The damping constant (herein, a Gilbertdamping coefficient) is referred to as a physical constant showing astrength of damping of precession of magnetization of the magnetic body.When the damping constant is small, the magnetization of the independentmagnetic body 60 is easily affected by the high frequency magneticfield, and oscillation of the magnetization can be increased.

The independent magnetic body 60 initially receives a signal from thefirst signal line 20, propagates the signal to the magnetoresistanceeffect element 10, and amplifies the signal. When the damping constantof the independent magnetic body 60 is small, the magnetization of theindependent magnetic body 60 readily precesses due to the high frequencymagnetic field generated in the first signal line 20. As a result, theindependent magnetic body 60 can apply a large magnetic field to themagnetization free layer 12 of the magnetoresistance effect element 10.

Rare earth element iron garnets (RIG) are known as materials having aninsulating property and a small damping constant. Yttrium iron garnet(YIG) among RIG is preferable. YIG has highly magnetic characteristicseven in a thin film and a small magnetic loss even in a high frequencyband.

A volume of the independent magnetic body 60 is preferably 100 times ormore a volume of the magnetization free layer 12, or preferably 1000times or more the volume of the magnetization free layer 12. A magneticmoment of the magnetic body is determined by a product of the saturationmagnetization Ms and the volume of the magnetic body. For this reason,when the volume of the magnetic body is increased, a magnetic moment ofthe magnetic body is increased, and an output signal is increased.

The output signal is a resistance value variation of themagnetoresistance effect element 10. For this reason, the principle ofincreasing the volume of the magnetization free layer 12 of themagnetoresistance effect element 10 is usual. However, the magnetizationfree layer 12 is a component of the magnetoresistance effect element 10,and it is difficult to increase the volume.

On the other hand, since the independent magnetic body 60 is presentindependently from other circuit components, the volume can be freelyset. In addition, the magnetization of the magnetization free layer 12precesses due to the influence of the precession of the magnetization ofthe independent magnetic body 60. That is, when a volume of theindependent magnetic body 60 is increased, the independent magnetic body60 can produce a large magnetic field, and the magnetization of themagnetization free layer 12 can be greatly changed.

The independent magnetic body 60 is disposed at a position where thehigh frequency magnetic field from the first signal line 20 can bereceived and the magnetization of the magnetization free layer 12 isaffected by the magnetic field. For this reason, the independentmagnetic body 60 may be disposed at any position above or below themagnetoresistance effect element 10 in the lamination direction (anupward/downward direction in FIG. 1) and an in-plane direction (aleftward/rightward direction in FIG. 1) crossing the laminationdirection. In order to efficiently apply the magnetic field in which themagnetization of the independent magnetic body 60 is generated to themagnetization free layer 12, the independent magnetic body 60 ispreferably disposed between the first signal line 20 and themagnetoresistance effect element 10. In addition, from a viewpoint ofeasy manufacture of the magnetoresistance effect device 100, theindependent magnetic body 60 is preferably installed above the firstsignal line 20 (a side opposite to the magnetoresistance effect element10).

<Magnetic Field Application Mechanism>

The magnetic field application mechanism 50 applies an external magneticfield to the independent magnetic body 60 and modulates a resonancefrequency of the independent magnetic body 60. The signal output fromthe magnetoresistance effect device 100 fluctuates due to the resonancefrequency of the independent magnetic body 60. For this reason, in orderto vary the output signal, a magnetic field application mechanism ispreferably further provided.

The magnetic field application mechanism 50 is preferably disposed inthe vicinity of the independent magnetic body 60. The magnetic fieldapplication mechanism 50 is configured as, for example, an electromagnettype or a stripline type that can variably control an applied magneticfield intensity using either a voltage or a current. In addition, themagnetic field application mechanism 50 may be configured by acombination of an electromagnet type or a stripline type that canvariably control the applied magnetic field intensity and a permanentmagnet configured to supply only a constant magnetic field.

[Function of Magnetoresistance Effect Device]

When the high frequency signal is input to the magnetoresistance effectdevice 100 from the first port 1, the high frequency currentcorresponding to the high frequency signal flows through the firstsignal line 20. The high frequency current flowing through the firstsignal line 20 applies a high frequency magnetic field to theindependent magnetic body 60.

The magnetization of the independent magnetic body 60 oscillates greatlywhen the high frequency magnetic field applied by the first signal line20 is close to the resonance frequency of the independent magnetic body60. The phenomenon is a ferromagnetic resonance phenomenon.

The magnetization of the independent magnetic body 60 produces amagnetic field. The magnetization of the magnetization free layer 12 ofthe magnetoresistance effect element 10 is moved by receiving aninfluence of the magnetic field produced by magnetization of theindependent magnetic body 60. That is, when the magnetization of theindependent magnetic body 60 is greatly oscillated, the producedmagnetic field of the independent magnetic body 60 is also greatlyvaried, and the magnetization of the magnetization free layer 12 isgreatly oscillated.

When the oscillation of the magnetization free layer 12 is increased, aresistance value variation in the magnetoresistance effect element 10 isincreased. The resistance value variation of the magnetoresistanceeffect element 10 is output from the second port 2 as a potentialdifference between the lower electrode 14 and the upper electrode 15.

That is, when the high frequency signal input from the first port 1 isclose to the resonance frequency of the independent magnetic body 60, afluctuation amount of the resistance value of the magnetoresistanceeffect element 10 is large, and a large signal is output from the secondport 2. On the other hand, when the high frequency signal has deviatedfrom the resonance frequency of the independent magnetic body 60, afluctuation amount of a resistance value of the magnetoresistance effectelement 10 is small, and most of the signal is not output from thesecond port 2. That is, the magnetoresistance effect device 100functions as a high frequency filter through which only a high frequencysignal having a specified frequency can selectively pass.

In this way, the magnetoresistance effect device 100 oscillates themagnetization of the independent magnetic body 60 using theferromagnetic resonance, and outputs the oscillation of themagnetization of the magnetization free layer 12 pulled by theoscillated magnetization as a signal mainly. Meanwhile, the highfrequency magnetic field generated in the first signal line 20 ispartially applied to also the magnetization free layer 12. For thisreason, the magnetization of the magnetization free layer 12 may beoscillated independently from the magnetization of the independentmagnetic body 60. Therefore, in order to increase the accuracy of thesignal output from the magnetoresistance effect device 100, it ispreferable to take the resonance frequency of the magnetization freelayer 12 into consideration.

The resonance frequency is varied by the effective magnetic field in themagnetic body. An effective magnetic field H_(eff) in the magnetic bodyis expressed by the following equation when an external magnetic fieldapplied to the magnetic body is H_(E), an anisotropic magnetic field inthe magnetic body is H_(k), an anti-magnetic field in the magnetic bodyis H_(D), and an exchange coupling magnetic field in the magnetic bodyis H_(EX).H _(eff) =H _(E) +H _(k) +H _(D) +H _(EX)  (1)

For this reason, the resonance frequency of the independent magneticbody 60 and the resonance frequency of the magnetization free layer 12may not coincide with each other. Hereinafter, a case in which theresonance frequency of the independent magnetic body 60 and theresonance frequency of the magnetization free layer 12 coincide witheach other and a case in which they do not coincide with each other willbe described in detail.

First, the case in which the resonance frequency of the independentmagnetic body 60 and the resonance frequency of the magnetization freelayer 12 coincide with each other will be described. FIG. 2 is a viewshowing a relation of an oscillation amplitude and an output signal withrespect to a period of the high frequency magnetic field applied to theindependent magnetic body 60 and the magnetization free layer 12. FIG.2(a) shows an oscillation amplitude of the independent magnetic body 60,FIG. 2(b) shows an oscillation amplitude of the magnetization free layer12, and FIG. 2(c) shows an output signal output from themagnetoresistance effect device 100.

The magnetization of the independent magnetic body 60 has a largeferromagnetic resonance at the resonance frequency f₀. For this reason,as shown in FIG. 2(a), the magnetization of the independent magneticbody 60 close to the resonance frequency f₀ shows a large oscillation,and shows almost no oscillation at other frequencies.

In addition, the magnetization of the magnetization free layer 12 isgreatly oscillated by being affected by the magnetic field produced bythe magnetization of the independent magnetic body 60. In addition, themagnetization free layer 12 is also affected by the magnetic fieldoutput from the first signal line 20. Even when a high frequencymagnetic field applied to the magnetoresistance effect element 10 by thefirst signal line 20 is close to the resonance frequency of themagnetization free layer 12, the magnetization of the magnetization freelayer 12 is greatly oscillated.

As shown in FIG. 2(b), a resonance frequency f₀ of the magnetizationfree layer 12 and a resonance frequency f₀ of the independent magneticbody 60 coincide with each other. For this reason, as shown in FIG.2(b), the magnetization of the magnetization free layer 12 is greatlyoscillated only at the resonance frequency f₀.

The magnetoresistance effect device 100 outputs the resistance valuevariation of the magnetoresistance effect element 10. The resistancevalue variation of the magnetoresistance effect element 10 is generatedby a relative variation between magnetization directions of themagnetization fixed layer 11 and the magnetization free layer 12. Forthis reason, the magnetoresistance effect device 100 outputs a largesignal at the resonance frequency f₀ on which the magnetization of themagnetization free layer 12 is greatly oscillated.

Next, a case in which a resonance frequency of the independent magneticbody 60 and a resonance frequency of the magnetization free layer 12 aredifferent will be described. FIG. 3 is a view showing a relation of anoscillation amplitude and an output signal with respect to a period of ahigh frequency magnetic field applied to the independent magnetic body60 and the magnetization free layer 12. FIG. 3(a) shows an oscillationamplitude of the independent magnetic body 60, FIG. 3(b) shows anoscillation amplitude of the magnetization free layer 12, and FIG. 3(c)shows an output signal output from the magnetoresistance effect device100.

The magnetization of the independent magnetic body 60 is a largeferromagnetic resonance at the resonance frequency f₀. For this reason,as shown in FIG. 3(a), the magnetization of the independent magneticbody 60 shows a large oscillation around the resonance frequency f₀, andshows almost no oscillation at another frequency.

Meanwhile, the magnetization of the magnetization free layer 12 isoscillated by receiving an influence from the independent magnetic body60 and an influence from the first signal line 20. The magnetization ofthe independent magnetic body 60 is oscillated at the resonancefrequency f₀, and produces a magnetic field. The magnetic fieldoscillates the magnetization of the magnetization free layer 12. As aresult, the magnetization of the magnetization free layer 12 isoscillated at the resonance frequency f₀.

In addition, the magnetization of the magnetization free layer 12 isoscillated even around the resonance frequency f₁ of the magnetizationfree layer 12. The oscillation is generated as the high frequencymagnetic field applied to the magnetoresistance effect element 10 by thefirst signal line 20 causes the magnetization and the ferromagneticresonance of the magnetization free layer 12.

Accordingly, as shown in FIG. 3(b), the magnetization of themagnetization free layer 12 is oscillated at the resonance frequency f₀of the independent magnetic body 60 and a resonance frequency f₁ of themagnetization free layer 12. For this reason, as shown in FIG. 3(c), themagnetoresistance effect device 100 outputs a large signal at theresonance frequency f₀ of the independent magnetic body 60 and theresonance frequency f₁ of the magnetization free layer 12.

In this way, there is a different in the output signal between when theresonance frequency of the independent magnetic body 60 and theresonance frequency of the magnetization free layer 12 coincide witheach other and when they do not coincide with each other.

When the resonance frequency of the independent magnetic body 60 and theresonance frequency of the magnetization free layer 12 coincide witheach other, the magnetization of the magnetization free layer 12 isgreatly oscillated by receiving an influence obtained by overlapping theinfluence from the independent magnetic body 60 and the influence fromthe first signal line 20. That is, it is advantageous that, when theresonance frequencies coincide with each other, a signal output from themagnetoresistance effect device 100 is increased.

Meanwhile, when the resonance frequency of the independent magnetic body60 and the resonance frequency of the magnetization free layer 12 aredifferent from each other, the magnetoresistance effect device 100capable of outputting two signals can be realized. In addition, it isalso possible to determine one output signal by decreasing one of thesignals output to the outside using the low pass filter.

When the low pass filter is used, the resonance frequency f₀ of theindependent magnetic body 60 is preferably smaller than the resonancefrequency f₁ of the magnetization free layer 12, and it is preferable touse the low pass filter configured to allow a frequency smaller than theresonance frequency f₁ of the magnetization free layer 12 to passtherethrough. When the effective magnetic field in the independentmagnetic body 60 is smaller than the effective magnetic field in themagnetization free layer 12, the resonance frequency f₀ of theindependent magnetic body 60 may be smaller than the resonance frequencyf₁ of the magnetization free layer 12 (see Equation (1)).

The magnetization free layer 12 has a small volume and a small magneticmoment. For this reason, an influence such as heat or the like is easilyexerted, and a thermal fluctuation or the like exerts an influence tothe oscillation of the magnetization of the magnetization free layer 12.It is said that the influence of the thermal fluctuation is increasedaround the resonance frequency f₁ of the magnetization free layer 12.That is, the output signal around the resonance frequency f₁ of themagnetization free layer 12 shown in FIG. 3(c) includes a large amountof noises. Since the signal including a large amount of noises isblocked by the low pass filter, only an output signal having a smallamount of noises (an output signal around the resonance frequency f₀ ofthe independent magnetic body 60) can be extracted.

Since the low pass filter is used in this way, an influence of thenoises can be minimized. Meanwhile, when the magnetic moment of theindependent magnetic body 60 is sufficiently larger than the magneticmoment of the magnetization free layer 12, an influence applied to themagnetization of the magnetization free layer 12 by the independentmagnetic body 60 is increased, and an influence applied to themagnetization of the magnetization free layer 12 by the first signalline 20 is decreased. That is, an output signal around the resonancefrequency f₀ of the independent magnetic body 60 in FIG. 3(b) isincreased, and an output signal around the resonance frequency f₁ of themagnetization free layer 12 is decreased. For this reason, even when thenoise is not blocked using the low pass filter, the noise can bedecreased to a level that can be sufficiently neglected. This is alsosimilar to the case in which the resonance frequency of the independentmagnetic body 60 and the resonance frequency of the magnetization freelayer 12 coincide with each other.

<Modulation of Resonance Frequency>

A frequency selected by the magnetoresistance effect device 100 can bemodulated by varying a resonance frequency of the magnetization freelayer 12. The resonance frequency is varied by the effective magneticfield in the magnetization free layer 12.

As shown in Equation (1), the effective magnetic field in themagnetization free layer 12 is affected by an external magnetic fieldH_(E). A magnitude of the external magnetic field H_(E) can be adjustedby the magnetic field application mechanism 50. FIG. 4 is a view showinga relation between a frequency of a high frequency signal input to themagnetoresistance effect device 100 and an amplitude of a voltage outputtherefrom when a direct current applied to the magnetoresistance effectelement 10 is constant.

When an arbitrary external magnetic field is applied to the independentmagnetic body 60, the resonance frequency of the independent magneticbody 60 is varied by receiving an influence of the external magneticfield. The resonance frequency at this time is fb1. Since the resonancefrequency of the independent magnetic body 60 is fb1, an amplitude of anoutput voltage when the frequency of the high frequency signal input tothe magnetoresistance effect device 100 is fb1 is increased (see FIG. 2and FIG. 3). For this reason, a graph of a plot line 100 b 1 shown inFIG. 4 is obtained.

Next, when the applied external magnetic field is increased, aninfluence of the external magnetic field is received and the resonancefrequency is shifted from fb1 to fb2. Here, the frequency at which theamplitude of the output voltage is increased is shifted from fb1 to fb2.As a result, a graph of a plot line 100 b 2 shown in FIG. 4 is obtained.In this way, the magnetic field application mechanism 50 can adjust aneffective magnetic field H_(eff) applied to the independent magneticbody 60, and modulate the resonance frequency.

Meanwhile, the magnetic field application mechanism 50 applies amagnetic field to both of the independent magnetic body 60 and themagnetoresistance effect element 10. For this reason, even when theresonance frequency of the independent magnetic body 60 and theresonance frequency of the magnetization free layer 12 can besimultaneously modulated, it is difficult to vary a relationship betweenthe resonance frequencies. That is, it is difficult to vary a frequencydifference between the resonance frequency f₀ and the resonancefrequency f₁ in FIG. 3(c). Here, a means configured to independentlymodulate only the resonance frequency of the magnetization free layer 12will be described.

A first means is to provide a bias magnetic layer configured to apply anexternal magnetic field to the magnetization free layer 12 of themagnetoresistance effect element 10. A size of the magnetoresistanceeffect element 10 is about several hundreds of nm, and a thickness ofthe magnetization free layer 12 is about several nm. For this reason, inorder to apply a magnetic field to the magnetization free layer 12without exerting an influence to the independent magnetic body 60, asource having an extremely small magnetic field is needed.

A bias magnetic layer is a magnetic film having magnetism. The biasmagnetic layer is obtained by laminating a magnetic film on the vicinityof the magnetization free layer 12. The bias magnetic layer can apply amagnetic field to the magnetization free layer 12 without exerting aninfluence to the independent magnetic body 60. When a magnetic field isapplied to the magnetization free layer 12 by the bias magnetic layer,the resonance frequency f₁ of the magnetization free layer 12 isincreased. As a result, a frequency difference between the resonancefrequency f₀ of the independent magnetic body 60 and the resonancefrequency f₁ of the magnetization free layer 12 can be increased. Whenthe frequency difference therebetween is increased, isolation of thesignal is facilitated by the low pass filter or the like.

Next, a second means is to vary a current density of a direct currentapplied to the magnetoresistance effect element 10 from the power supply41. FIG. 5 is a view showing a relation between a frequency of a highfrequency signal input to the magnetoresistance effect device 100 and anamplitude of a voltage output therefrom when an external magnetic fieldapplied to the magnetoresistance effect element 10 is constant. Here, adirect current flows to the magnetoresistance effect element 10, andthere is no influence to the independent magnetic body 60. For thisreason, “an amplitude of an output voltage” disclosed herein is obtainedaccording to the resonance frequency f₁ of the magnetization free layer12 (see FIG. 3(b)), and is not obtained according to the resonancefrequency f₀ of the independent magnetic body 60.

The output voltage output from the second port 2 of themagnetoresistance effect device 100 is expressed as a product of aresistance value oscillated in the magnetoresistance effect element 10and a direct current flowing through the magnetoresistance effectelement 10. When the direct current flowing through themagnetoresistance effect element is increased, an amplitude (an outputsignal) of the output voltage is increased.

In addition, when a direct current amount flowing to themagnetoresistance effect element 10 is varied, a state of themagnetization in the magnetization free layer 12 is varied, andmagnitudes of an anisotropic magnetic field H_(k), an anti-magneticfield H_(D) and a magnetic exchange coupling magnetic field H_(EX) inthe magnetization free layer 12 are varied. As a result, the resonancefrequency is decreased when the direct current is increased. That is,when a direct current amount is increased as shown in FIG. 5, theamplitude of the output voltage is shifted from a plot line 100 a 1 to aplot line 100 a 2. In this way, since the amount of the current appliedto the magnetoresistance effect element 10 from the power supply 41 isvaried, the resonance frequency of the magnetization free layer 12 canbe modulated. When the resonance frequency f₁ of the magnetization freelayer 12 can be modulated, a frequency difference between the resonancefrequency f₀ of the independent magnetic body 60 and the resonancefrequency f₁ of the magnetization free layer 12 can be increased, andisolation of the signal is facilitated by the low pass filter or thelike.

<Another Use>

In addition, while the case in which the magnetoresistance effect deviceis used as the high frequency filter as described above has beenexemplarily provided, the magnetoresistance effect device may be used asa high frequency device such as an isolator, a phase shifter, anamplifier (an amp), or the like.

When the magnetoresistance effect device is used as the isolator, asignal is input from the second port 2. Since there is no signal outputfrom the first port 1 even when the signal is input from the second port2, the device functions as the isolator.

In addition, when the magnetoresistance effect device is used as thephase shifter, in the case in which the output frequency band is varied,it is focused to a frequency of an arbitrary point in the outputfrequency band. When the output frequency band is varied, since a phasein a specified frequency is varied, the device functions as the phaseshifter.

In addition, when the magnetoresistance effect device is used as theamplifier, the resistance value variation of the magnetoresistanceeffect element 10 is increased. The resistance value variation of themagnetoresistance effect element 10 is increased as the direct currentinput from the power supply 41 becomes a predetermined magnitude or moreor the independent magnetic body 60 increases the high frequencymagnetic field applied to the magnetoresistance effect element 10. Whenthe resistance value variation of the magnetoresistance effect element10 is increased, the signal output from the second port 2 is larger thanthe signal input from the first port 1, and functions as an amplifier.

As described above, the magnetoresistance effect device 100 according tothe first embodiment may function as a high frequency device such as ahigh frequency filter, an isolator, a phase shifter, an amplifier, orthe like.

As described above, the magnetoresistance effect device 100 according tothe embodiment moves the magnetization of the magnetization free layer12 using the magnetic field generated due to the oscillation of themagnetization of the independent magnetic body 60. Since the independentmagnetic body 60 having a large magnetic moment is used, themagnetization of the magnetization free layer 12 can reduce an influenceof the noise generated by the oscillation due to the thermal fluctuationor the like.

In addition, when the resonance frequency of the independent magneticbody 60 and the resonance frequency of the magnetization free layer aredifferent from each other, the output signal around the resonancefrequency of the magnetization free layer that can be easily affected bythe noise can be blocked by the low pass filter or the like, and themagnetoresistance effect device 100 having a smaller amount of noise canbe realized.

Hereinafter, while the preferred embodiment of the present disclosurehas been described in detail, the present disclosure is not limited tothe specific embodiment and various modifications and changes may bemade without departing from the spirit of the present disclosuredisclosed in the following claims.

For example, the magnetoresistance effect device may have a plurality ofmagnetoresistance effect elements 10. FIG. 6 is a view schematicallyshowing an example of a circuit configuration of a magnetoresistanceeffect device including a plurality of magnetoresistance effectelements.

In a magnetoresistance effect device 101 shown in FIG. 6, threemagnetoresistance effect elements (a first magnetoresistance effectelement 10 a, a second magnetoresistance effect element 10 b and a thirdmagnetoresistance effect element 10 c) are disposed with respect to oneindependent magnetic body 60. The first magnetoresistance effect element10 a, the second magnetoresistance effect element 10 b and the thirdmagnetoresistance effect element 10 c are disposed in series in a closedcircuit constituted by the power supply 41, the output signal line 30,the third signal line 31 and the ground G.

The magnetoresistance effect elements are similarly oscillated by themagnetic field applied from the one independent magnetic body 60. Forthis reason, the signal output from the second port 2 is a sum of theoutput signals from the magnetoresistance effect elements 10. That is,according to the magnetoresistance effect device 101 shown in FIG. 6,the output signal can be increased.

In addition, FIG. 7 is a view schematically showing another example of acircuit configuration of a magnetoresistance effect device including aplurality of magnetoresistance effect elements. In a magnetoresistanceeffect device 102 shown in FIG. 7, three magnetoresistance effectelements (a first magnetoresistance effect element 10 a, a secondmagnetoresistance effect element 10 b and a third magnetoresistanceeffect element 10 c) are disposed with respect to one independentmagnetic body 60 and arranged parallel to the direct current applicationterminal 40 to which the power supply 41 is connected.

Also in the case of the serial arrangement or the parallel arrangement,the output voltage variation reads a variation of a combined resistanceof the elements. In the case of the parallel arrangement, a combinedresistance value is reduced as the number of the parallelly arrangedsensors is increased. Accordingly, in the case of the parallelarrangement, while the output signal is not increased, accuracy of theoutput signal can be improved. That is, the magnetoresistance effectdevice 102 shown in FIG. 7 can obtain a signal having a small amount ofnoise.

In addition, FIG. 8 is a view schematically showing another example of acircuit configuration of a magnetoresistance effect device including aplurality of magnetoresistance effect element. A magnetoresistanceeffect device 103 shown in FIG. 8 has a structure in which themagnetoresistance effect elements are combined in the parallelarrangement and the serial arrangement with respect to the power supply41. In addition, FIG. 9 is a perspective view of another example of acircuit configuration of a magnetoresistance effect device including aplurality of magnetoresistance effect elements. In FIG. 9, twomagnetoresistance effect elements 10 that are arranged in parallel aredisposed in series to four sets with respect to a power supply (notshown).

As shown in FIG. 8 and FIG. 9, when the magnetoresistance effectelements 10 that are arranged in series and in parallel with the powersupply 41 are combined, advantages thereof may be overlapped. While aninternal resistance of the magnetoresistance effect elements 10 cannotbe neglected in the serial arrangement, an influence of the internalresistance can be reduced by combining the sensors 10 in the parallelarrangement. In addition, the case in which the power supply 41 and thedirect current application terminal 40 are provided each solely has beenexemplarily described in the above-mentioned example, a plurality ofpower supplies 41 and a plurality of direct current applicationterminals 40 may be provided. In this case, the plurality of powersupplies 41 and the plurality of direct current application terminals 40are connected to the magnetoresistance effect elements 10, respectively,and a direct current or a direct current voltage is applied to each ofthe magnetoresistance effect elements 10. In addition, even in thiscase, the one power supply 41 and the one direct current applicationterminal 40 may be shared by the plurality of magnetoresistance effectelements 10.

In addition, in FIG. 6 to FIG. 9, while the case in which the pluralityof magnetoresistance effect elements are installed with respect to theone independent magnetic body 60 has been described, the independentmagnetic body 60 may be disposed with respect to each of themagnetoresistance effect elements.

FIG. 10 is a view schematically showing an example of a circuitconfiguration of a magnetoresistance effect device in which a pluralityof magnetoresistance effect elements and a plurality of independentmagnetic bodies are provided, and one independent magnetic body isinstalled with respect to one magnetoresistance effect element.

The resonance frequencies of the independent magnetic bodies 60installed on the magnetoresistance effect elements 10 are preferablydifferent from each other. The resonance frequency of the independentmagnetic body 60 can be controlled by varying a shape in a plan viewwhen seen in the lamination direction. When the plurality of independentmagnetic bodies 60 having different resonance frequencies are used, theindependent magnetic bodies 60 are oscillated at the resonancefrequencies, respectively, and the magnetoresistance effect elementsinstalled in the vicinity thereof show large resistance value variationsat the resonance frequencies, respectively. Then, a value obtained bysumming them is output from the second port 2. For this reason, afrequency in a range in which the resonance frequencies overlap is aselected frequency of a magnetoresistance effect device 104, and a bandof the selected frequency is widened.

The magnetic field application mechanism 50 may be one shared by theindependent magnetic bodies 60 (see FIG. 10) or may be installed at eachof them. When the magnetic field application mechanisms 50 are installedwith respect to the magnetoresistance effect elements, respectively,while integration of the magnetoresistance effect device 104 isdecreased, a degree of setting freedom of a selected frequency of themagnetoresistance effect device 104 is increased. While the case of theserial arrangement with respect to the power supply 41 has been shown inFIG. 10, it is also the same in any one of parallel arrangement, and acombination of serial arrangement and parallel arrangement.

In addition, FIG. 11 is a view schematically showing another example ofa circuit configuration of a magnetoresistance effect device including aplurality of magnetoresistance effect elements. A magnetoresistanceeffect device 105 shown in FIG. 11 includes a first magnetoresistanceeffect element 10 a, a second magnetoresistance effect element 10 b, afirst independent magnetic body 60 a and a second independent magneticbody 60 b.

A high frequency magnetic field generated in the first independentmagnetic body 60 a is applied to the first magnetoresistance effectelement 10 a, and a high frequency magnetic field generated in thesecond independent magnetic body 60 b is applied to the secondmagnetoresistance effect element 10 b. The magnetization of the firstindependent magnetic body 60 a produces a high frequency magnetic fieldby receiving the high frequency magnetic field generated in the firstsignal line 20, and the magnetization of the second independent magneticbody 60 b produces a high frequency magnetic field by receiving the highfrequency magnetic field generated in the output signal line 30.

A high frequency signal input to the magnetoresistance effect device 105from the first port 1 is filtered by the first magnetoresistance effectelement 10 a. The filtered high frequency signal is output from theoutput signal line 30. The high frequency signal is filtered by thesecond magnetoresistance effect element 10 b, and output to the outsideof the magnetoresistance effect device 105 from the second port 2. Thatis, a signal input from the first port 1 of the magnetoresistance effectdevice 105 is filtered by two times until the signal is output from thesecond port 2. Accordingly, according to the magnetoresistance effectdevice 105, filtering accuracy of the high frequency signal can beimproved.

In addition, the number of the magnetoresistance effect elements is notlimited to two, and a larger number of elements may be provided. In thiscase, a high frequency magnetic field from the first signal line isapplied to at least one of the plurality of magnetoresistance effectelements, and a high frequency magnetic field from the output signalline output from another magnetoresistance effect element is applied tothe remaining magnetoresistance effect elements. As the number of themagnetoresistance effect elements is increased, filtering accuracy ofthe high frequency signal is further improved.

In addition, even in the configuration of the magnetoresistance effectdevice 105 shown in FIG. 11, one independent magnetic body may beprovided for each of the magnetoresistance effect elements. FIG. 12 is aview schematically showing another example of a circuit configuration ofa magnetoresistance effect device including a plurality ofmagnetoresistance effect elements. In a magnetoresistance effect device106 shown in FIG. 12, one independent magnetic body 60 is disposed withrespect to the first magnetoresistance effect element 10 a and thesecond magnetoresistance effect element 10 b.

Magnetization of the second magnetoresistance effect element 10 b isoscillated by receiving influences of the first signal line 20, theindependent magnetic body 60 and the output signal line 30. A highfrequency current flowing through the output signal line 30 is filteredby the first magnetoresistance effect element 10 a. That is, a highfrequency magnetic field fed back by the first magnetoresistance effectelement 10 a is applied to the second magnetoresistance effect element10 b. When the feedback is repeated, the same effect as that when thefiltering is performed a plurality of times (FIG. 11) is obtained,accuracy of the output signal can be improved.

EXAMPLES Example 1

Magnitudes of an output voltage and a noise output voltage output fromthe magnetoresistance effect device were measured through simulation. Ithas been confirmed that the simulation has a good correspondencerelation with measured values.

FIG. 13 is an enlarged schematic view of a major part of amagnetoresistance effect device of Example 1. The magnetoresistanceeffect element 10 was formed in a cylindrical shape having a diameter of200 nm and a thickness of 25 nm. In addition, a thickness of the lowerelectrode 14 was 100 nm and a thickness of the upper electrode 15 was 50nm. Then, the independent magnetic body 60 was disposed between thefirst signal line 20 and the upper electrode 15 via insulating layers61. The independent magnetic body 60 was formed to have a thickness of200 nm and a length of 10 μm. A thickness of the insulating layer 61 was50 nm. Further, the first signal line 20 was formed to have a thicknessof 100 nm and a width of 1 μm.

In addition, the saturation magnetization Ms of the independent magneticbody 60 was 0.77 kOe, and a damping constant α was 0.015. The conditioncorresponds to a case in which NiFe (permalloy) is used as theindependent magnetic body 60. Further, the saturation magnetization Msof the magnetization free layer of the magnetoresistance effect element10 was 1.5 kOe, and the damping constant α was 0.02. The conditioncorresponds to the case in which CoFeB is used as the magnetization freelayer. In addition, a bias magnetic field H_(ext) of 192 Oe was appliedto the independent magnetic body 60 and the magnetization free layer bythe external magnetic field application mechanism.

When a voltage of 5 mV (−36 dBM as electric power) was input to themagnetoresistance effect device and a characteristic impedance was 50Ω,the output voltage and the noise output electric power were calculatedthrough simulation. The result is shown in FIG. 14 and FIG. 15. FIG. 14shows a result of the output voltage of the magnetoresistance effectdevice according to Example 1, and FIG. 15 shows a result of the noiseoutput electric power of the magnetoresistance effect device accordingto Example 1.

As shown in FIG. 14, in the output voltage of the magnetoresistanceeffect device according to Example 1, two peaks were seen at 3.4 GHz and4.8 GHz. The peak at 3.4 GHz is provided according to the ferromagneticresonance of the independent magnetic body 60, and the peak at 4.8 GHzis provided according to the ferromagnetic resonance of themagnetization free layer. Since the magnitude of the saturationmagnetization Ms differs in the independent magnetic body 60 and themagnetization free layer, the ferromagnetic resonance frequencies arealso different from each other.

In the noise output voltage, as shown in FIG. 15, a peak was seen at 4.8GHz. The peak is considered to be caused by a large thermal fluctuationof the magnetization around the resonance frequency of the magnetizationfree layer. Meanwhile, the independent magnetic body 60 has a volume32,000 times the magnetization free layer. For this reason, themagnetization is rarely shaken under the influence of heat and the like,and almost no noise derived from the independent magnetic body 60 wasobserved.

That is, when the low pass filter through which a frequency of 4.0 GHzor less can pass is installed in the magnetoresistance effect device ofExample 1, a high frequency signal having a small amount of noise can beextracted.

Comparative Example 1

In Comparative example 1, output characteristics of themagnetoresistance effect device in which an independent magnetic body isnot provided were obtained. FIG. 16 is an enlarged schematic view of amajor part of the magnetoresistance effect device of Comparativeexample 1. The output voltage and the noise output electric power werecalculated through simulation under the same condition as in Example 1except that the independent magnetic body is removed and the biasmagnetic field H_(ext) is 100 Oe. The result is shown in FIG. 17 andFIG. 18. FIG. 17 shows a result of an output voltage of themagnetoresistance effect device according to Comparative example 1, andFIG. 18 shows a result of a noise output electric power of themagnetoresistance effect device according to Comparative example 1.

In Comparative example 1, as the bias magnetic field H_(ext) is changed,a ferromagnetic resonance frequency of the magnetization free layer wasvaried to 3.1 GHz. In addition, since a distance between the firstsignal line and the magnetization free layer is decreased because theindependent magnetic body is not present, the magnetization free layerreceives a larger high frequency magnetic field from the first signalline.

Comparing the result (FIG. 14) of the output voltage around 3 GHz of themagnetoresistance effect device of Example 1 and the result (FIG. 17) ofthe output voltage around 3 GHz of the magnetoresistance effect deviceof Comparative example 1, while the output voltage of Example 1 was 7.0mV, the output voltage of Comparative example 1 was 1.4 mV. That is,when a driving region of the magnetoresistance effect device is 3 GHz,Example 1 shows output characteristics five times Comparative example 1.In addition, comparing the results of the noise output voltage around 3GHz, the noise output electric power (FIG. 15) of Example 1 was 1/100 ofthe noise output electric power (FIG. 18) of Comparative example 1.

Comparative Example 2

Comparative example 2 was under the same condition as Comparativeexample 1 except that the bias magnetic field H_(ext) was 192 Oe. FIG.19 shows a result of an output voltage of the magnetoresistance effectdevice according to Comparative example 2, and FIG. 20 shows a result ofa noise output electric power of the magnetoresistance effect deviceaccording to Comparative example 2.

As shown in FIG. 19 and FIG. 20, both of a position of a peak of theoutput voltage and a position of a peak of the noise output electricpower were shifted from the position of the peak in Comparative example1 (shown by a dot line). That is, as the magnitude of the bias magneticfield H_(ext) from the external magnetic field application mechanism isvaried, the ferromagnetic resonance frequency of the magnetization freelayer can be varied. In addition, the ferromagnetic resonance frequencyof the magnetization free layer of Comparative example 2 was almostequal to the ferromagnetic resonance frequency of the magnetization freelayer in Example 1 because the magnitude of the applied bias magneticfield H_(ext) is equal.

Example 2

Example 2 is distinguished from Example 1 in that the magnitude of thebias magnetic field H_(ext) applied to the magnetization free layer was392 Oe. Further, the magnitude of the bias magnetic field H_(ext)applied to the independent magnetic body 60 was 192 Oe. Then, the outputvoltage and the noise output electric power output from themagnetoresistance effect device of Example 2 were calculated throughsimulation. The results are shown in FIG. 21 and FIG. 22. FIG. 21 showsa result of an output voltage of the magnetoresistance effect deviceaccording to Example 2, and FIG. 23 shows a result of a noise outputelectric power of the magnetoresistance effect device according toExample 2.

As shown in FIG. 21, in the output voltage of the magnetoresistanceeffect device according to Example 2, two peaks were seen at 3.4 GHz and6.7 GHz. The peak at 3.4 GHz is provided according to the ferromagneticresonance of the independent magnetic body 60, and the peak at 6.7 GHzis provided according to the ferromagnetic resonance of themagnetization free layer. Since the magnitude of the bias magnetic fieldH_(ext) applied to the independent magnetic body 60 is the same as inExample 1, the ferromagnetic resonance frequency of the independentmagnetic body 60 was not varied. On the other hand, since the magnitudeof the bias magnetic field H_(ext) applied to the magnetization freelayer is increased, the ferromagnetic resonance frequency of themagnetization free layer was shifted.

In addition, a peak position of the noise output electric power shown inFIG. 22 was shifted. This is because a thermal fluctuation of themagnetization is increased around the resonance frequency of themagnetization free layer. As the peak position of the noise outputvoltage is shifted, a value of the noise output voltage around 3 GHz canbe decreased to be smaller than that in Example 1 (FIG. 15).

Example 3

Example 3 is distinguished from Example 2 in that a plurality ofmagnetoresistance effect elements 10 are provided. FIG. 23 is anenlarged schematic view of a major part of a magnetoresistance effectdevice according to Example 3. The magnetoresistance effect deviceaccording to Example 3 has four groups arranged in series, and eachgroup has four magnetoresistance effect elements 10 arranged in parallelbetween the upper electrode 15 and the lower electrode 14. Then, theoutput voltage and the noise output electric power output from themagnetoresistance effect device of Example 3 were calculated throughsimulation. The results are shown in FIG. 24 and FIG. 25. FIG. 24 showsa result of an output voltage of the magnetoresistance effect deviceaccording to Example 3, and FIG. 25 shows a result of a noise outputelectric power of the magnetoresistance effect device according toExample 3.

As shown in FIG. 24, as the plurality of magnetoresistance effectelements 10 are installed, the output voltage in Example 3 was fourtimes the output voltage (FIG. 21) in Example 2. On the other hand, asshown in FIG. 25, the magnitude of the noise output electric power inExample 3 was not different from the output voltage (FIG. 22) in Example3.

While preferred embodiments of the invention have been described andillustrated above, it should be understood that these are exemplary ofthe invention and are not to be considered as limiting. Additions,omissions, substitutions, and other modifications can be made withoutdeparting from the spirit or scope of the present disclosure.Accordingly, the invention is not to be considered as being limited bythe foregoing description, and is only limited by the scope of theappended claims.

EXPLANATION OF REFERENCES

-   -   1 First port    -   2 Second port    -   10 Magnetoresistance effect element    -   11 First ferromagnetic layer (magnetization fixed layer)    -   12 Second ferromagnetic layer (magnetization free layer)    -   13 Spacer layer    -   14 Lower electrode    -   15 Upper electrode    -   20 First signal line    -   30 Output signal line (second signal line)    -   31 Third signal line    -   40 Direct current application terminal    -   41 Power supply    -   42 Inductor    -   50 Magnetic field application mechanism    -   60 Independent magnetic body    -   61 Insulating layer    -   G Ground    -   100, 101, 102, 103, 104, 105, 106 Magnetoresistance effect        device    -   M₁₁, M₁₂ Magnetization    -   RF High frequency magnetic field

What is claimed is:
 1. A magnetoresistance effect device comprising: amagnetoresistance effect element having a first ferromagnetic layer, asecond ferromagnetic layer, and a spacer layer sandwiched between thefirst ferromagnetic layer and the second ferromagnetic layer; a firstport configured for a high frequency signal to be input; a second portconfigured for a high frequency signal to be output; a first signal lineconnected to the first port and configured to generate a high frequencymagnetic field when a high frequency current corresponding to the highfrequency signal input into the first port flows; a second signal line;a direct current application terminal to which a power supply is able tobe connected to cause a direct current to flow to the magnetoresistanceeffect element in a lamination direction; and an independent magneticbody configured to receive a high frequency magnetic field generated inthe first signal line to oscillate magnetization and apply a magneticfield generated through the magnetization to the magnetoresistanceeffect element, wherein the magnetoresistance effect element isconnected to the second port via the second signal line, and the directcurrent application terminal is connected to the magnetoresistanceeffect element.
 2. The magnetoresistance effect device according toclaim 1, wherein a resonance frequency of the independent magnetic bodyis smaller than a resonance frequency of the first ferromagnetic layerand the second ferromagnetic layer.
 3. The magnetoresistance effectdevice according to claim 2, further comprising: a low pass filterconfigured to reduce a part of a signal output to the outside, whereinthe low pass filter allows a frequency smaller than the resonancefrequency of the first ferromagnetic layer and the second ferromagneticlayer to pass therethrough.
 4. The magnetoresistance effect deviceaccording to claim 1, wherein a volume of the independent magnetic bodyis 100 times or more a volume of the first ferromagnetic layer or thesecond ferromagnetic layer.
 5. The magnetoresistance effect deviceaccording to claim 2, wherein a volume of the independent magnetic bodyis 100 times or more a volume of the first ferromagnetic layer or thesecond ferromagnetic layer.
 6. The magnetoresistance effect deviceaccording to claim 1, wherein a damping constant of the independentmagnetic body is 0.005 or less.
 7. The magnetoresistance effect deviceaccording to claim 2, wherein a damping constant of the independentmagnetic body is 0.005 or less.
 8. The magnetoresistance effect deviceaccording to claim 1, wherein the independent magnetic body is aninsulating material.
 9. The magnetoresistance effect device according toclaim 1, wherein the independent magnetic body is an electricalconductor.
 10. The magnetoresistance effect device according to claim 1,further comprising: a magnetic field application mechanism configured toapply an external magnetic field to the independent magnetic body, andmodulate a resonance frequency of at least one of the independentmagnetic body, the first ferromagnetic layer and the secondferromagnetic layer.
 11. The magnetoresistance effect device accordingto claim 1, further comprising: a bias magnetic layer configured toapply an external magnetic field to the first ferromagnetic layer or thesecond ferromagnetic layer of the magnetoresistance effect element, andmodulate a resonance frequency of the first ferromagnetic layer or thesecond ferromagnetic layer.
 12. The magnetoresistance effect deviceaccording to claim 1, wherein a plurality of magnetoresistance effectelements are provided, and the plurality of magnetoresistance effectelements are disposed with respect to the one independent magnetic body.13. The magnetoresistance effect device according to claim 1, wherein aplurality of magnetoresistance effect elements and a plurality ofindependent magnetic bodies are provided, and each independent magneticbody is disposed with respect to one magnetoresistance effect element,respectively.
 14. The magnetoresistance effect device according to claim12, wherein at least some of the plurality of magnetoresistance effectelements are arranged parallel to each other.
 15. The magnetoresistanceeffect device according to claim 12, wherein at least some of theplurality of magnetoresistance effect elements are arranged in series.16. The magnetoresistance effect device according to claim 12, whereineach of the plurality of magnetoresistance effect elements has an outputsignal line through which a high frequency current output from themagnetoresistance effect element flows, and at least one of the outputsignal lines is disposed at a position where a high frequency magneticfield is applied to the independent magnetic body configured to apply amagnetic field to at least one of the plurality of magnetoresistanceeffect elements.
 17. The magnetoresistance effect device according toclaim 13, wherein at least some of the plurality of magnetoresistanceeffect elements are arranged parallel to each other.
 18. Themagnetoresistance effect device according to claim 13, wherein at leastsome of the plurality of magnetoresistance effect elements are arrangedin series.
 19. The magnetoresistance effect device according to claim13, wherein each of the plurality of magnetoresistance effect elementshas an output signal line through which a high frequency current outputfrom the magnetoresistance effect element flows, and at least one of theoutput signal lines is disposed at a position where a high frequencymagnetic field is applied to the independent magnetic body configured toapply a magnetic field to at least one of the plurality ofmagnetoresistance effect elements.
 20. A high frequency device using themagnetoresistance effect device according to claim 1.